In the American mind, he's often viewed as a crazed dictator (the New York Post called him a "ranting loon" during his 2008 UN visit), and he may have added to that image with his comments this afternoon.

In a speech that appealed to common values between Christianity and Islam and that spoke positively of the prophets Jesus and Moses as well as Muhammad, Mr. Ahmadinejad quickly veered into the sort of territory that has infuriated his opponents and at times even left supporters at home scratching their heads in frustration.

This time it wasn't Holocaust denial so much as Ahmadinejad apparently lending credence to theories that the 9/11 attacks on the United States were abetted by the US government. A speech that some had hoped would signal a greater willingness to cooperate with the international community over his country's nuclear program and lead to greater US-Iran dialogue saw the US delegation walk out in protest soon after he started speaking.

Ahmadinejad said it was possible that the US had arranged the 9/11 attacks as part of a propaganda effort to help domestic business interests and the state of Israel, and called for the UN to investigate the attacks on New York and Washington 9 years after they were organized and carried out by Al Qaeda.

Why Ahmadinejad may tone it down

Ahmadinejad has certainly established a penchant for making statements that sound outrageous to Westerners, be they ones that question the reality of the Holocaust or a comment a few years ago that was interpreted by many as a call for Israel to be wiped off the map.

But Ahmadinejad's tone has been somewhat more measured of late, today's comments notwithstanding, reflecting international sanctions over Iran's nuclear program that are biting Iran's economy, pressure from Iran's ruling elite not to increase the country's isolation, and perhaps Ahmadinejad's own desire to negotiate a nuclear deal with Western powers to bolster his domestic standing.

That puts Ahmadinejad in the middle of a series of overlapping conflicts.

Hated by reformers, suspected by clerics

To the US and its closest allies, he's the face of a regime whose civilian nuclear program is suspected of being a cover for the construction of a nuclear bomb. Regionally, he's a symbol of Muslim resistance of Israel and opposition to the US.

And at home, he's both hated by reformers who believe he stole the last presidential election and viewed with suspicion by parts of the clerical establishment, who think he's trying to increase his power at their expense.

"Ayatollah Ali Khamenei, holds the true levers of power, especially on political and national security matters [in Iran]," Mohamad Bazzi, a fellow at the Council on Foreign Relations, wrote on Ahmadinejad's UN visit this week. "But Mr. Ahmadinejad's role has changed: he has seized far more authority than he had a few years ago and he is working tirelessly to eliminate his political opponents. It has become much harder to ignore his antics and poisonous rhetoric."

The engineer who excelled in school

That Ahmadinejad would become such a central international figure would have been unthinkable just seven years ago, when the PhD engineer and civil servant was selected by Tehran's conservative city council as mayor.

He was born in 1956 into a working class family (his father was an iron worker) in the city of Garmsar, about 50 miles south of Tehran. The family moved to the capital when he was a boy, and he excelled academically.

In the 1980s, he worked with the Revolutionary Guard during the Iran-Iraq war, and later held a number of provincial government appointments.

Ahmadinejad's rise to power

The platform for Ahmadinejad's rise came as something of a fluke.

In 1999, reformists swept to power in the Tehran city council election, but failed to bring meaningful change to their constituents in the following three years.

The 2003 election was largely abandoned by reformist voters and had dismal turnout – less than 15 percent – which delivered a city government of hard-line conservatives. It was they who placed Ahmadinejad – a former basiji in the Revolutionary Guard, a minor figure in Iran and virtually unknown internationally – in power.

From mayor to president

Ahmadinejad's leadership of Iran's largest city gave him a bully pulpit, and he consistently projected the image of a simple, pious man, which struck a chord with Iranians tired of the corruption of many of the clerics and politicians that had ruled them since the 1979 Islamic Revolution.

In 2005, backed by many conservatives, Ahmadinejad won the presidency over Hashami Rafsanjani, a cleric who favored a more conciliatory tone to the outside world, after a campaign in which he painted his opponent as corrupt. He was the first non-cleric to become president in 24 years, setting up what has become a power struggle between Ahmadinejad and the clerical establishment.

A populist, he plays far better in Iran's smaller towns and cities than he does among the elites in Tehran. Though he often talks of Iran's global importance and demands international respect, his promise to deliver jobs to the poor and listen to the working class is largely responsible for his popularity.